tapping heat stakes



#7

Back in October[1] Djj posted an account of threading the heat stakes inside a 15c-LE to reassemble it after repairing some keys. Would someone who knows what the inside of a 32sii looks like comment on whether or not a trick like that could be used to reassemble a 32sii? That approach would be much more preferable than using stubs of metal clipped from an old chip and then epoxying the PCB down.

[1] http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv020.cgi?read=200353#200353


#8

You really don't need to attach metal and epoxy to the posts.
Just use 10 min expoxy in gel and a heavy weight to pressure the parts together.
Cut the melting head of posts off the PCB, do what you need to the PCB, put it back; prepare some epoxy and, quickly put a drop over each hole. The epoxy will hold the pcb after cured. You will need to make the most well distributed pressure on pcb as you can during at least two hours, so, use something heavy and small plastic or wood pins to support it over pcb.
No need to drill anything with the risks this proccess carry on.
Best new year!!!
artur mario jr at gmail dot com


#9

My reason for wanting to tap the heat stake stubs is because it makes subsequent disassembly easy. With the use of epoxy, that wouldn't be the case.


#10

Quote:
With the use of epoxy, that wouldn't be the case.

Sure it is - I did it and it all works just fine. The PCB fits/snaps pretty well on the heat stakes and would stay in place even without sealing it with epoxy. Little drops are easy to remove if need be to open it again. Worked on mine - no problem for over a month now.

Cheers,

Reth

#11

Quote:
My reason for wanting to tap the heat stake stubs is because it makes subsequent disassembly easy. With the use of epoxy, that wouldn't be the case.

Yea I really wouldn't recommend using epoxy as suggested here as
it will bond far too well to the pcb and be a nightmare to remove
should you have cause to subsequently free the pcb. Actually
it probably isn't the best adhesive choice either for a number of
reasons.

The best method I've found to reseat ABS heat stakes is with
acetone. Acetone is an aggressive ABS solvent and spectacularly
volatile. As such it creates an excellent weld bond and flashes
off quite rapidly. The net effect is you can "glue" a new head
onto a stake post in about 30 seconds, during which the head
can be held under pressure to restore joint compression.
I've built a small ad-hoc jig
to apply pressure to the joint until the solvent dissipates but
a drill press quill with a weight on the quill lever works
as well.

A little acetone goes a long way and some experimentation on
scrap ABS might be a good ideal to get the feel for its
characteristics. One issue with pure acetone is its low
viscosity which can cause it to run away from the intended
target in this application. I thought to experiment by
dissolving some scrap ABS in acetone to create a more viscous
adhesive which should stay put far better, but have been doing
ok with straight acetone applied sparingly.

On that last note I'd recommend using a syringe with about a 30
gauge needle to apply the stuff to the stake posts as you wouldn't
want unintended ABS exposed to the solvent as I've alarmed
earlier.


#12

I've done similar things with ABS and acetone with a slight modification. I dripped acetone on ABS shavings and stirred until I got a paste and then used that to make the bond. That fixes the low viscosity problem. It's particularly useful for filling gaps.

Edited: 31 Dec 2011, 3:04 a.m.


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